DBR Laser Frequency Noise Reduction via Feedback Control
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Solution Overview
Problem
DBR lasers exhibit relatively large frequency noise and linewidth, which is challenging to reduce due to their complex structure, especially in coherent communication systems where amplitude- and frequency-modulated information is transmitted.
Innovation Solution
A laser device with a Distributed Bragg Reflector (DBR) section, phase section, and gain section, equipped with a feedback control system that detects frequency fluctuations in the output light beam and adjusts tuning currents to the DBR and phase sections to counteract these fluctuations, thereby reducing frequency noise and linewidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If DBR laser structure is used to achieve wide frequency tuning range, then adaptability is improved, but frequency noise and linewidth increase
Solution Approach 1:
The patent implements a feedback control system that detects frequency fluctuations in the laser output and generates corrective signals to counteract these fluctuations. A frequency discriminator converts frequency deviations into voltage signals, which are then amplified and fed back to the laser diode to stabilize the output frequency, thereby reducing frequency noise and linewidth while maintaining the wide tuning capability of the DBR structure
Solution Approach 2:
The patent introduces a frequency discriminator as an intermediary component that mediates between the laser output and the feedback control circuit. This discriminator converts the optical frequency fluctuations into electrical voltage signals that can be processed by the control circuit, enabling indirect control of the laser frequency without directly modifying the laser cavity structure
2Reliability
If feedback control circuit is added to reduce frequency noise, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent employs a feedback control mechanism where frequency fluctuations are detected and corrected in real-time. The feedback signal is derived from the laser's own output through a frequency discriminator, creating a self-regulating system that improves frequency stability without requiring external complex control infrastructure
Solution Approach 2:
The laser system performs self-diagnosis and self-correction of frequency deviations. The frequency discriminator monitors the laser output and generates correction signals automatically, allowing the system to maintain frequency stability autonomously without external intervention or complex external control systems
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively suppresses frequency noise across a wide range of lasing frequencies, achieving a narrower linewidth and improved stability in DBR lasers, without affecting laser light intensity and simplifying the control circuitry compared to DFB lasers.
Implementation Method 1
a frequency noise detector in communication with said feedback control means, arranged to detect a frequency fluctuation in a light beam output from the laser
Implementation Method 2
the feedback control means is arranged to feed a respective variable electric feedback signal to at least one of said at least one DBR section and said at least one phase section of the laser, so that the output laser frequency is altered in response to a variation in the feedback signal
Data Source
AI summary
A laser device (100) includes a laser (110; 210; 310; 410; 510) in turn including at least one Distributed Bragg Reflector (DBR) section (111), at least one phase section (112) and at least one gain section (113), further including a laser control element (150), a feedback control element (140) and a frequency noise discriminator (130,131), which feedback control element is arranged to feed a variable feedback signal to at least one of the at least one DBR section and the at least one phase section of the laser, so that the output laser frequency is altered in response to a variation in the feedback signal or the combination of respective feedback signals, whereby the feedback signal or combination of respective feedback signals is varied as a function of the detected frequency fluctuation so as to counteract the detected frequency fluctuation.